In order to provide components that are designed appropriately for the loads occurring, it is known to produce semifinished products known as “tailored blanks” with different material properties, which consist of different materials or material thicknesses to be welded to one another that ensure the various mechanical properties. It is additionally known, as an alternative to this, to achieve the various different mechanical properties by a microstructural transformation. Used for this purpose are hardenable steel materials, which are partially brought to a temperature above the Ac1 temperature point or the Ac3 temperature point and are subsequently rapidly cooled, so that the austenitic structure that is above the Ac1 temperature or the Ac3 temperature is at least partially transformed into a martensitic structure. In the case for example of manganese-boron steels, this martensitic structure can then provide tensile strengths of up to 2000 MPa in the hardened state.
Japanese patent application JP 2002-020854 A discloses for example a method for producing a shaped metal body that consists of two different profiles, the component consisting of a first profile and a second profile, one of the profiles having undergone a hardening process. However, the component produced in this way and designed appropriately for the loads occurring still has a weld seam and must therefore still undergo a number of working steps to provide different mechanical properties in one component. To this extent, the cost-effectiveness of producing components with mechanical properties appropriate for the loads occurring that provide the mechanical properties by microstructural transformations can be improved.
Therefore, a need exists for low-cost method methods and devices for partially hardening semifinished products that have at least partially the cross-sectional form of an open or closed profile, so that it is possible to dispense with complete hardening of the semifinished product or the provision of a welded connection to provide various mechanical properties.